Morossi, Carlo

Contact Email: morossi@ts.astro.it
Institute: Osservatorio Astronomico di Trieste
via G.B. Tiepolo 11 I-34131 Trieste (Italy)
First Coauthor: Mariagrazia Franchini
Institute: Osservatorio Astronomico di Trieste
Second Coauthor: Maria Lucia Malagnini
Institute: Dipartimento di Astronomia, Universita` degli Studi di Trieste, Italy
Subject Area: Stellar Atmospheres, Circumstellar Material
Waveband: Multi-wavelength
Technique: Spectroscopy
Presentation: Oral Contribution: Thursday
Title: Far-Ultraviolet continuum as a diagnostic of the temperature structure in the atmosphere of G-type Stars.
Abstract: Investigations of IUE ultraviolet spectra of field G and K type stars (Morossi et al. 1993, Morossi et al. 1997, Franchini et al. 1998a) showed that the spectral energy distributions (SED's) of cool stars present a significant excess in the UV with respect to the fluxes predicted by the atmosphere models characterized by a monotonic decrease of temperature. HST, IUE and visual observations are combined to construct accurate SED's to be used to derive empirical estimate of the temperature distribution in the atmosphere of G-type stars. Template objects are used to compare pure LTE model predictions with those from semi-empirical structures designed for the solar case (Vernazza et al. 1981). Particular attention is devoted to the determination of the position of the temperature minimum layer by computing "semi-empirical Tmin models" (Morossi et al. 1993 and Franchini et al. 1998b) and schematic models of stellar atmospheres made of hydrogen only (Simonneau & Crivellari 1988, Crivellari & Simonneau 1994). PS. Please note that the complete list of co-authors includes also Miguel Chavez (INAOE, Puebla Mexico).